1. Field of the Invention
The present invention relates to a condensation system for use in a power plant including a steam generator and a steam turbine, and more particularly to a condensation system comprising at least one side stream condenser defining therein first and second hot wells with the first hot well receiving therein condensate produced by condensing steam exhausted from the steam turbine.
2. Description of the Prior Art
A condensation system of the kind referred to above is disclosed in Japanese Patent Laying-Open No. 61589/81 laid open for public inspection on May 27, 1981. The condensation system disclosed in the Japanese patent laying-open publication includes a condensation feed line having one end thereof connected to the first hot well of the side stream condenser and the other end connected to the second hot well thereof, and a condensate pump device provided in the condensate feed line for forcedly delivering the condensate from the first hot well to the second hot well through the condensate feed line. A first purification device comprising a filteration type demineralizer is disposed in the condensate feed line downstream of the condensate pumping device for removing impurities from the condensate flowing through the condensate feed line. A second purification device comprising a mixed-bed type demineralizer is disposed in the condensate feed line downstream of the first purification device, for removing impurities from the condensate flowing through the condensate feed line. An air-withdrawer is connected to the condensate feed line in parallel thereto downstream of the second purification device, for condensing steam which is utilized to actuate a steam ejector so as to withdraw incondensable gas out of the side stream condenser. A gland-steam condenser is connected to the air-withdrawer in parallel thereto, for condensing steam enclosed within gland portions of the steam turbine and valves.
In the condensation system of the prior art described above, corroded substances contained in the condensate received in the first hot well of the side stream condenser and corroded substances produced in a portion of the condensate feed line upstream of the first and second purification devices are removed by the first and second purification devices.
However, corroded substances produced in a portion of the condensate feed line downstream of the second purification device, and corroded substances produced in the gland-steam condenser, the air-withdrawer, the main condensate pump device and the main condensate feed line having provided therein the main condensate pump device are introduced into the steam generator through the main condensate feed line as they are.
If the power plant is a thermoelectric power plant, the corroded substances introduced into the steam generator cause scale deposited on a boiler of the steam generator to be increased to decrease the performance of the boiler.
If the power plant is a nuclear power plant, the corroded substances introduced into a nuclear reactor of the steam generator become radionuclides, and the surface dose rate from the condensate feed lines and the like is increased to increase the exposure dose on operators during the inspection and maintenance. One of the serious or significant problems in the nuclear power plant of today is the improvement in quality of the condensate. A great deal of effort is concentrated on the countermoves to this problem and the reduction in exposure dose is the problem which is required to be solved by all means. Accordingly, in the condensation system of the prior art, it is a serious or significant problem that a considerable amount of corroded substances is introduced into the nuclear reactor, that is, the total iron concentration in the condensate is high and the condensate is poor in quality.